Good video, though I’d like to add some comments, premised with the fact I’ve never taken an agronomy class. 🙂
Labile carbon mosly comes from air and top soil, driven by photosynthesis and oxygen reduction. It doesn’t need sunlight and water but they certainly form the dominant reactions. Sulfur and iron are also important for redox of carbon compounds, especially the deeper in the soil you get and the lower the energy state it is in. Without sulfur and iron, carbon lifeforms can’t oxidize certain carbon compounds and utilise them.
It doesn’t have to take 40-60 years to convert carbon in compost if the C:N ratio is in a working carbon priming range. Carbon priming of soils occurs between a C:N of 12:1 and 80:1 by microbes. The problem is that most composts use up all their nitrogen before field application and when the carbon in compost is applied to soils, microbes take up nitrogen and oxygen from the soil to break it down for use and thereby reduce plant available nitrogen and oxygen. Which is why here in Australia “Next Gen” compost that have slow release fertilzer added to it show excellent results.
Several plant species are also able to exude organic acids in response to toxic elements like Aluminium that tends to bind soil aggregates and increase soil density reducing plant air and water availability. Why it’s good to have a mix of plant species.
Organic acids in the carboxyl group like vinegar (acetic acid) have been shown in low doses to improve drought tolerance, effectively helping plants oxidize material for consumption. This is basically akin to Steve Solomon’s approach in Gardening Without Irrigation, by doing the work for the plants.
Sulfonic acids bring with them sulfur groups and an even stronger acid to break down material. One study on sterile meteroities that landed in deserts showed sulfur in the meteorite being used by indigenous microbes to break that meteorite down.
Other organic acids like phenols however can impede seedling root growth, so I’d only recommend them on established crops. Anaerobic practises like bokashi create these phenolic compounds.
Fungi also produce organic acids, and the more soil carbon you have the more fungi, the more carbon cycling.
As for disease, the less soil carbon you have, the more predatory organisms you have, like nematodes and fungi. When fungi don’t have enough carbon available they prey on plants to get that carbon. When there aren’t enough fungi to keep the nematodes in check, the nematodes prey on plants.
Everything needs that precious carbon to live above all else.
In the right environment, livestock can also play an important carbon cycling role with these organic acids and regenerative farming practices.
The integrated crop–livestock system showed the highest concentrations of dissolved soil organic C (78 μg C g−1 soil) as well as phenolic compounds (1.5 μg C g−1 soil), reducing sugars (23 μg C g−1 soil), and amino acids (0.76 μg N g−1 soil), and these components were up to 3-fold greater than soils under the other systems. However, soil β-glucosidase activity in the integrated crop–livestock system was significantly lower than the other systems and appeared to reflect the inhibitory role of soluble phenolics on this enzyme